Apparently an Ontario musician posted the 16,777,215th comment on Slashdot last night, thus blowing up the comment table on the popular site. Slashdot has its comment index as an unsigned mediumint in MySQL, which maxes out at 2^24, thus putting the maximum size of the table at 16,777,216 rows. Given how Slashdot increments those figures (two databases, one using odd figures, one even), the above comment in the odd table tipped Slashdot over its comment limit.
So, blame Canada. Again.